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• Two mononuclear Dy complexes based on the luminescent chromophore coumarin ligand have been synthesized and structurally characterized. • Both Dy(III) complexes exhibited a magnetic relaxation phenomenon attributable to their large magnetic anisotropy. • Both two Dy(III) complexes displayed the distinctive emission spectra. Lanthanide luminescent single-molecule magnets (SMMs) serve as a kind of multifunctional molecular materials that have attracted extensive attention. Herein, a novel chromophore coumarin ligand 7-(diethylamino)-(2‑hydroxy-3-methoxybenzylidene)-2-oxo-2-chromene-3-carbohydrazide (Hvalcoumarin) is designed to construct the luminescent Dy(III) complexes. Two Dy complexes 1 ([D y (valcoumarin)(DMF) 2 C l 2 ]·(CHCl 3)) and 2 [Dy(valcoumarin)(DMF) 2 (NO 3) 2 ] were synthesized based on the luminescent chromophore coumarin ligand (Hvalcoumarin). X-ray crystallography reveals that the Dy(III) center in complex 1 adopts a hepta-coordinated arrangement by a distorted pentagonal bipyramidal geometry. In contrast, complex 2 exhibits a nine-coordinate arrangement by a spherical capped square antiprism geometry. Magnetic investigations reveal that 1 and 2 exhibit a slow magnetic relaxation phenomenon. Furthermore, the luminescent spectra of 1 and 2 display the characteristic emission profiles associated with Dy(III) spectra. Moreover, theoretical calculations also demonstrated the relaxation dynamics of 1 and 2. The results furnish a potent avenue for the acquisition of multifunctional molecular materials with magnetic and luminescent properties. [Display omitted] Two Dy(III) complexes based on a novel coumarin ligand have been reported, and both of them exhibited slow magnetic relaxation behavior and luminescent properties. [ABSTRACT FROM AUTHOR]